1. Field of the Invention
This disclosure relates to liquid crystal display devices and more particularly to an assembly having the optical sensing frame in which a control unit for driving an optical sensing frame is integrated with a control unit of a display panel.
2. Discussion of the Related Art
In general, a touch panel, providing an interface between an information and communication device, which uses various kinds of displays, is an input unit which enables interface with the device as the user touches a screen with a hand or a pen.
Because such a device can be used by touching a button or icon displayed on a display device with a finger in a conversational and intuitive way, the touch panel is applicable to many fields, such as automatic teller machines in banks and public agencies, various medical apparatus, tour and major facility guidance, and traffic guidance.
In touch panel displays, there are resistive type touch panels, micro capacitive touch glass, ultrasonic wave touch glass, infrared type touch panels, and so on.
The resistive type touch panel has two transparent conductive layers wherein a lower layer thereof is formed of glass or plastic coated with a conductive material, and an upper layer thereof is formed of a film coated with a conductive material. The two layers are spaced by micro printed spacers and electrically insulated. The resistive type touch panel is a device which involves in a change of resistance at each of an upper plate (X-axis) and a lower plate (Y-axis) when the upper plate is touched with a hand or a touch pen when in a state a fixed voltage is being applied to the two layers. In this instance, an X (the upper plate) and a Y (the lower plate) positions of which resistances are changed thus are calculated by a controller to display the positions on a monitor or input as data.
The micro capacitive touch glass has a transparent glass sensor coated with a thin conductive material. Therefore, an electrode pattern is printed along a periphery of a conductive layer precisely and has a transparent vitreous protective film placed closely on the conductive coating for protecting and enclosing the sensor. In the micro capacitive touch glass, a voltage is applied to a screen, and an electrode pattern forms a low voltage field on a touch sensor surface through the conductive layer. When the finger touches the screen, a micro current flows at a touch point. A current from each corner is proportional to a distance from the corner to the finger, and a touch screen controller calculates ratios of current flows for finding a position at which the touch is made.
The ultrasonic wave touch glass displays are not affected by surface damage and do not wear or degrade at all in comparison to other products which are formed of 100% vitreous material, where such vitreous material displays can be destroyed even by small surface damage or wear. In such displays, a touch screen controller forwards a 5 MHz electric signal to a transducer to generate an ultrasonic wave, and the ultrasonic wave generated thus passes along a surface of the touch screen due to reflected rays. In the ultrasonic wave touch glass, if a user presses a surface of the touch screen, a portion of the ultrasonic wave passing through a pressed point is absorbed by the user, a signal lost thus is identified instantly by a controller owing to a received signal and a digital map, and based on this, coordinates of a point having a change of the signal presently are calculated. Such a series of steps are performed independently on X- and Y-axes.
The infrared type touch panel utilizes an attribute of the infrared ray in which the infrared ray cannot travel if the infrared ray is blocked by an obstacle because of the straight travel characteristics of the infrared ray. A portion having a pressure applied thereto cuts off the infrared rays in a transverse direction and a longitudinal direction, and X and Y coordinates of a cut off portion are read for sensing. An infrared ray light type identifies a touched position owing to cut off of an infrared ray scan light at a front of the touch panel. The infrared type touch panel has an infrared ray emitted from one side and received at an opposite side both of x and y axes to form a lattice of the infrared rays.
Though above display types have different advantages, the infrared type touch panel is preferred because of the minimal pressure applied to the touch panel, and because of the convenience of the arrangement.
A related art infrared type touch panel will be described with reference to the attached drawings.
FIG. 1 illustrates a plan view of a related art infrared type touch panel.
Referring to FIG. 1, the related art infrared type touch panel is provided with infrared sensors 5 mounted to adjacent two corners of the panel 10, and reflective plates 7 are mounted to three sides of the panel 10.
A touch to the infrared type touch panel is detected as follows. That is, lights from the infrared sensors 5 are reflected, lights cut off at the time of the touch are sensed, and angels thereof are calculated to perceive the location of the touch.
However, the infrared type touch panel has a dead zone with a range greater than a certain angle between the infrared sensors 5 in which the detection is not possible, making accuracy of the touch poor at a particular region. In order to correct this, the infrared sensors are positioned on far outsides of the corners of the liquid crystal display panel so that the dead zone is formed at an outer side of the liquid crystal panel. In this case, a touch panel having a size greater than the liquid crystal panel is required, resulting in an increased non-effective area, which does not contribute to display picture, thereby reducing the efficiency of the display device.
In general, the liquid crystal panel is separate from the touch panel. If it is intended to produce the touch, a work for assembling respective components and applying coordinates to the touch panel suitable to the liquid crystal panel and a work for securing the touch panel to a liquid crystal module are required.
The related art touch panel has disadvantages in that selection of accurate coordinates is difficult, and only one touch point can be perceived at one time. In other words, if two points on the touch panel are touched at a time, the touch panel fails to perceive this, or perceives one of the touch points touched first, thus causing an error.
The related art touch panel is formed separated from the liquid crystal panel, and requires a touch panel driving unit to have an additional PCB (Printed Circuit Board), and a connection between the touch panel driving unit and the touch panel, and connection between the touch panel driving unit and the liquid crystal panel driving unit. Moreover, since the PCBs of the liquid crystal panel driving unit and the touch panel driving unit are required to be mounted without overlap with one another, and these are required to be connected to a system for controlling the system, at least the touch panel driving unit and the liquid crystal panel are required to have connecting portions between the PCBs, the system and the touch panel driving unit and the liquid crystal panel for driving the touch panel driving unit and the liquid crystal panel respectively, which wiring connections are complex.
Since connection between the PCBs is required, a wiring structure thereof becomes complicated, and integrated circuits are duplicated between the PCBs, thus increasing the cost.
The infrared type touch panels have the following problems.
First, if two infrared cameras are provided, the dead zone takes place at a side adjacent to the two cameras, which requires providing a touch assembly of a size greater than the size of the liquid crystal panel. In this case, a space greater than the liquid crystal panel is required for mounting the touch assembly, making narrow bezel impossible.
Second, when sensing is made only with the two infrared cameras, a ghost image is formed when a multi-touch is made.
Third, since the PCB for driving the touch panel and the PCB for driving the liquid crystal panel are provided individually, the liquid crystal display device has no integrated structure. Therefore, connection among the touch panel, the PCB for driving the touch panel, and the PCB for driving the liquid crystal panel are required, and an assembly process for mounting is required.
Fourth, for example, in order to drive the infrared camera, a connection wiring structure is required for connecting the infrared camera to the PCB for driving the touch panel. Particularly, in view of position, a connection wiring between the infrared camera positioned at an upper side of the liquid crystal panel and the touch panel driving unit positioned on the back side of a lower side of the liquid crystal panel becomes lengthy, which may cause electromagnetic interference.
Fifth, the PCB for driving the touch panel and the PCB for driving the liquid crystal panel are provided individually, having duplicated ICs, which increases the cost.
Sixth, in a case of the touch assembly having two infrared cameras, resulting in a touch assembly larger than the liquid crystal panel, there is no small sized module available.